All clownfish females are the result of males undergoing a sex change, or protandric hermaphrodites as they are called. In most host anemones a small harem of clownfish are present. Generally, this harem contains a single female, a single male, and several juvenile fish. The female is the most dominant member of the harem, and her constant attention to the harem ensures that the male does not develop into a female. When the female becomes absent from the harem, the male will assume the role of the female. Once a female, the fish cannot revert back to male. Both the male and female inhibit the sex change tendency of the juveniles. This phenomenon is often referred to as "psychophysical castration." When the male undergoes sex change and becomes a female, the juveniles will battle to determine who the most dominant member is. The winner will then grow testicles and become a male. These sex changes will occur in less than one month. In some instances, immigrating fish may disrupt this natural hierarchy. Some species (A. clarkii) have been noted to roam over 500 feet in search of another host anemone. In these cases, males and females may get thrown out of their host anemone by a stronger individual that left their original host anemone. Generally, these migrating specimens were displaced from their previous anemone in similar fashion. Juveniles will also migrate to nearby host anemones in hopes of moving up in the pecking order. In rare situations, juveniles may skip over the step of becoming a male, instead maturing from a juvenile into a female. This may occur if a male and female are not present in the host anemone, or a roaming juvenile is more dominant than the present female and male.
